In the field of telecommunications, wireless base stations include global positioning software (GPS) to synchronize among themselves. Installation and maintenance of GPS at each site is expensive. In dense urban environments, communication between the sites can be poor due to tall buildings and poor signal strength within them. Some base stations include dedicated backhaul timing circuits that are expensive. Other fields that require distributed precision time include packet switched telecommunications in metropolitan areas, control, test and measurement applications, and military systems.
In the aforementioned applications, the existing network, e.g. Ethernet, is used to accommodate the timing purposes as well as the traffic transport. To meet this requirement, Ethernet requires recovery of timing. Timing protocols, e.g. IEEE 1588 standard, can be implemented to recover time. Timing inaccuracies are introduced by the delays, delay asymmetries, and jitter from the following network related sources: physical layers, cables, and network devices, e.g. routers, switches, low-accuracy boundary clocks, and low-accuracy transparent clocks.
FIG. 1 illustrates a prior art system. A timing source, e.g. a grandmaster clock, communicates to two ordinary clocks via a series of network infrastructure components, e.g. switches, routers, repeaters, or low accuracy boundary clocks. In actual implementation, these are standard Ethernet switches and routers used establish network communications for the other devices shown. These devices introduce timing jitter that degrades the synchronization accuracy between the timing source and the ordinary clocks. One example is where the ordinary clocks are part of wireless micro-cell base stations within a large office building. In this case, the Ethernet forms the backhaul to the base station switch for data transmission. The synchronization is met with a separate and expensive time distribution system (not shown).